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Late last week coastal geologist Rip Kirby was on the seashore as part of an effort to detect oil by shining UV lights—widely used to spot blood at crime scenes—on Gulf beaches. The method, he hopes, will allow scientists and cleanup crews to tackle hard-to-spot oil, such as crude mixed with mud or light stains on sand, that's washed ashore from the sinking of the BP-leased Deepwater Horizon rig.

Under UV light, clean sand appears purple or black. Some minerals, such as calcium carbonate in seashells, glow blue, as does a shovel handle in the picture above.

Although hydrocarbons have long been known to fluoresce, or glow, under ultraviolet light, this may be the first time the technology has been used outside a lab to spot oil. "The use of UV light to identify [types of] oil is an industry-wide process," said Kirby, a graduate student at the University of South Florida. But "I've always seen it in a [lab] machine," he said.

"The first time I took the UV flashlight out on the beach to see if it would work, it was beyond my wildest dreams," Kirby said. "It was easy to see that there was oil on the beach ... the contamination was widespread."

Graduate student Kirby hopes that ultraviolet light can be used on beaches to guide oil-spill cleanup operations. The heavy-duty spotlight his team uses costs thousands of dollars, making it probably too expensive to supply to the tens of thousands of workers cleaning oil from Gulf beaches.

However, a U.S. $17 portable UV flashlight—like those used by bouncers to spot fake IDs—was also successful at spotting the oil. "You almost have to be right on top of the oil to see the orange fluorescence" with the inexpensive light, but it could suffice for beach cleanup work, Kirby said.

Before landing on the beach, the oil had become "weathered," made foamy and gooey by extended exposure to air and water.

One challenge of working with UV light—also a component of sunlight—is that it can damage eyesight.

"The damaging parts of sunlight aren't really the visible parts of the spectrum but the invisible ones," Kirby said. "That's why ophthalmologists say to wear UV-filtering sunglasses." Powerful UV spotlights such as the one being used in the above picture—which Kirby calls the "Klingon death ray"—are particularly dangerous, he said.

Boots worn by University of South Florida graduate student Katie Brusché are stained with yellow-brown tar from the Gulf oil spill, as seen under ultraviolet light in a long-exposure photograph. Under UV light, even lightly contaminated sand glows bright orange-yellow.

One challenge of cleaning up the oil is collateral contamination, including the transfer of oil via workers' boots, Kirby said.

"BP hasn't put cleaning stations at all the exits [to the beach], as required by federal law," he said. "People ... go back to the parking lot and scrape off [the oil]. Other people step in the brown gunky stuff," and the oil contamination spreads.

Kirby said he doesn't know of a more effective oil-detecting tool than ultraviolet light. For example, an odor detector wouldn't work, he said. "How are you going to smell it?" he asked, because the entire area will smell like oil, and pin-pointing a particular source would be difficult.

"You could get yourself a weiner dog that goes berserk from oil, but weiner dogs go berserk about anything, so it would be hard to tell," he joked.

Photograph by Chris Combs, National Geographic

Tar Patties, UV Light

Under an ultraviolet spotlight, the same tar patties glow yellow against the sand, which appears purple.

The ultraviolet light could make it possible to determine how long ago oil had washed up in a given region, Kirby said.

He said he saw that, under the special light, "oil that had just come in, floating on the ocean, was more of a greenish orange. The drier the oil got, the more orange it became." It's difficult, though, to precisely date the oil, because of other factors such as humidity.

It's not yet clear why the Gulf oil glows the colors that it does. Hydrocarbons can glow in a range of colors, from pink to orange, Kirby said.

He speculated that the oil may glow orange because of iron content, but the answer will have to wait until after the oil is analyzed in a lab.

Kirby questions why public officials haven't said precisely how toxic the oil is; this lack of information is cited by politicians as a reason to keep Pensacola Beach and other popular shores open, he said.

"It's like the mayor of Amity in Jawshere, only in slow motion," said Kirby, referring to the movie mayor who refused to close a shark-infested beach during the height of tourist season.

Photograph by Chris Combs, National Geographic

Footprints, UV Light

The same footprints, seen under ultraviolet light, are shown to be heavily contaminated by oil.

Kirby said that the best way to clean up oil of this nature could be so-called bioremediation.

Once the oil stops washing ashore in large quantities, such as if the leaking wellhead were to be capped, "you could spray microbes on it that would eat the oil and leave [the sand] in place," he said.

"The bacteria are naturally occurring. We just harvest them and grow a bunch in a 42-gallon [160-liter] barrel so we can spray it out in a food-rich environment."

Photograph by Chris Combs, National Geographic

"Clean" Sand, Normal Light

A patch of sand far from the water appears clean when lighted by a normal flashlight on a Pensacola, Florida-area beach.

As part of his research, coastal geology graduate student Kirby hopes to figure out whether there are particular wavelengths of ultraviolet light that would work best to detect the spilled oil. For example, low-wavelength ultraviolet lasers could scan entire beaches for oil, though workers would need protective eyewear.

Photograph by Chris Combs, National Geographic

"Clean" Sand, UV Light

A heavy-duty UV spotlight shows the same patch of sand to be contaminated with specks of oil, glowing yellow. The blue specks are likely naturally occurring seashell particles or minerals.

Kirby and research team leader Ping Wang think the oil seen here was spread by wind. Rolling grains of sand hit each other "like billiard balls," said Kirby, and briefly fly into the air.

With the ultraviolet spotlight, Kirby was able to see individual particles of oil-stained sand rolling along the beach.

"I am in this to clean up the damaged beach and see that it is done as efficiently as possible," he said. "BP could run out of assets just like anybody else, and I want to see this cleanup get done before then."

Photograph by Chris Combs, National Geographic

Oily Sand Blown Far

Many yards from the Gulf of Mexico, dunes at the Gulf Islands National Seashore appear dotted with constellations of oil-contaminated, glowing sand under ultraviolet light.

Describing similar dunes, Kirby said that "dried sand particles that were contaminated by oil were blowing into the dunes of the back beach. If you consider how much sand can be moved in a short period of time by wind, this is a big deal."

If clean-up workers on a beach are using a net to sift lumps of oil from sand, "clean sand goes through the oily net and gets coated with oil," he said. "You've contaminated another quart of sand in order to get a couple of ounces of oil out, and it'll end up in the [dunes]."